JP6060755B2 - Crucible for growing sapphire single crystal and method for producing the same - Google Patents

Description

  The present invention relates to a crucible for growing a sapphire single crystal used for growing a sapphire single crystal.

  In recent years, white LEDs have been widely used as lighting devices due to demands for energy saving and space saving. This white LED is configured by combining a blue LED in which a GaN-based semiconductor is formed on a sapphire single crystal substrate and a phosphor. For this reason, with the increase in demand for white LEDs, the demand for sapphire single crystal substrates has also increased rapidly. Further, since the cost reduction is required to use the white LED for general illumination, the sapphire single crystal substrate is also required to be reduced in price.

  Generally, a sapphire single crystal substrate is manufactured by cutting out a disk-shaped wafer from a sapphire single crystal ingot grown from a sapphire raw material melt (alumina melt). The sapphire single crystal is grown by pulling the single crystal from the melt, represented by the Czochralski method (rotary pulling method) and the EFG method (edge-defined film-fed growth method). The solidification pulling method and the method of solidifying the sapphire raw material melt in the crucible represented by the Bridgman method (vertical temperature gradient solidification method) and the VGF method (vertical temperature gradient solidification method). is there.

  Among these, the pulling method requires a space and a device for pulling up the grown sapphire single crystal, and the crystal growing device must be enlarged, and the initial investment cost increases. In contrast, the Bridgman method and the VGF method do not require the grown sapphire single crystal to be pulled up, so that the crystal growth apparatus can be reduced in size and simplified, and the initial investment cost can be reduced. Further, in the case of the pulling method, crystal growth in the c-axis direction, which is required as a sapphire single crystal substrate, is inefficient and not practical. For this reason, the growth is performed in the a-axis direction with high growth efficiency. In this case, the loss when cutting out the substrate in the c-axis direction from the obtained sapphire single crystal ingot becomes very large. On the other hand, in the case of the Bridgman method or the VGF method, the degree of freedom of crystal orientation for growth is high, and crystals in the c-axis direction can be efficiently grown. It is.

  When growing a sapphire single crystal by the Bridgman method or the VGF method, in order to solidify the sapphire raw material melt in the crucible, it is necessary to take out the solidified sapphire single crystal from the crucible. However, the solidified sapphire single crystal cannot be easily taken out from the crucible, and it is necessary to destroy the crucible. This is the practical application of the growth of the sapphire single crystal by the Bridgeman method or the VGF method. It is a cause that hinders.

On the other hand, when growing a sapphire single crystal, due to the high melting point (2040 ° C.) of alumina (Al ₂ O ₃ ) which is a raw material of sapphire, the crucible for melting alumina can withstand high temperatures of 2000 ° C. or higher. As shown in Japanese Patent Application Laid-Open No. 2008-239352, the materials are iridium (melting point: 2454 ° C.), rhenium (melting point: 3100 ° C.), tungsten (melting point: 3380 ° C.), molybdenum (Melting point: 2620 ° C.) or other high melting point metals or alloys thereof.

  Among these refractory metals, iridium (Ir), rhenium (Re), etc. have characteristics such as high melting point durability and chemical stability, but in addition to being very expensive, their thermal expansion coefficient is sapphire. Therefore, it is difficult to take out the sapphire single crystal from the crucible.

  In order to utilize the characteristics of iridium, JP 2007-119297 A proposes that the thickness of the thin iridium crucible be 0.3 mm or less. JP-A-7-034289 proposes forming an iridium plating layer on the surface of a crucible made of tungsten, molybdenum, tantalum, or an alloy thereof. According to these techniques, since the amount of iridium used can be suppressed, the production cost can be reduced.

  However, in the thin crucible made of iridium described in JP 2007-119297 A, the crucible is broken every time the sapphire single crystal is grown. Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-034289, the iridium plating layer is peeled off after growing the sapphire single crystal, so that it is difficult to reuse the crucible. Therefore, any crucible cannot be used repeatedly, and the fundamental solution of the problem that the crucible is expensive is not intended.

  Under these circumstances, as a crucible material used for growing a sapphire single crystal by the Bridgman method or the VGF method, tungsten, which is a relatively low price among refractory metals and has a smaller thermal expansion coefficient than the sapphire single crystal. Attention has been focused on (W) and molybdenum (Mo). For example, in JP 2011-42560 A, focusing on the difference between the linear expansion coefficient of the crucible and the linear expansion coefficient in the direction perpendicular to the growth axis (c-axis) of the sapphire single crystal, tungsten, molybdenum, or these An alloy crucible has been proposed.

  Among these, it is described that a crucible made of molybdenum allows a single crystal to be taken out without destroying the crucible, although cracks occur on the outer periphery of the solidified sapphire single crystal. However, since the difference in thermal expansion coefficient between molybdenum and sapphire is not sufficient, in practice, it is often impossible to take out a single crystal without destroying the crucible. On the other hand, a crucible made of tungsten or an alloy of tungsten and molybdenum has been described that there is no problem with respect to the coefficient of thermal expansion and that a high-quality sapphire single crystal can be obtained. The crucible may need to be broken.

  As described above, even when a crucible made of tungsten, molybdenum, or an alloy thereof is used, the growth of sapphire single crystals by the Bridgeman method or the VGF method has not been put into practical use in an industrial process. It is a fact.

JP 2008-239352 A JP 2007-119297 A JP 7-034289 A JP 2011-042560 A

  In view of the above problems, the present invention makes it possible to easily take out a grown sapphire single crystal without destroying the crucible even when the sapphire single crystal is grown by the Bridgeman method or the VGF method. An object of the present invention is to provide a crucible for growing a sapphire single crystal at low cost.

The crucible for growing a sapphire single crystal of the present invention is made of tungsten or a tungsten alloy having a melting point of 2400 ° C. or more and a thermal expansion coefficient at 2040 ° C. of 8 × 10 ⁻⁶ / ° C. or less, and the inner peripheral surface of the crucible Among these, during the growth of the sapphire single crystal, at least a portion that is in contact with the upper surface of the sapphire raw material melt, the component constituting the tungsten or the tungsten alloy, and 5 mass% or more of the metal element M (M is Pt, An anti-adhesion layer made of an alloy with one or more elements selected from Pd, Re, Rh, and Ir), and the tungsten content on the surface of the anti-adhesion layer is 20% by mass or more, and The content of the metal element M is 20% by mass or more, and the thickness thereof is 0.05 μm to 50 μm. The anti-adhesion layer may be formed on the entire inner surface of the crucible.

  The tungsten alloy is preferably made of an alloy of tungsten and molybdenum.

  The thickness of the anti-adhesion layer is preferably 0.1 μm to 10 μm.

  The tungsten content on the surface of the anti-adhesion layer is preferably 20% by mass to 50% by mass.

  The tungsten content in the alloy of tungsten and molybdenum is preferably 30% by mass or more.

  According to the present invention, a sapphire single crystal growth crucible that enables easy removal of a sapphire single crystal after growth without destroying the crucible in the growth of a sapphire single crystal by the Bridgeman method or the VGF method. It can be provided at a cost. In addition, when the sapphire single crystal is taken out, it is possible to effectively prevent the sapphire single crystal from being cracked, and the productivity of the sapphire single crystal can be improved. .

FIG. 1 is a schematic sectional view showing an example of an embodiment of a crucible for growing a sapphire single crystal of the present invention. FIG. 2 is an enlarged view of a portion A in FIG. FIG. 3 is a schematic sectional view showing an example of another embodiment of the crucible for growing a sapphire single crystal of the present invention. FIG. 4 is a graph showing the temperature dependence of the thermal expansion coefficients of alumina (Al ₂ O ₃ ), tungsten and molybdenum.

  Even when the sapphire single crystal is grown by using a crucible made of molybdenum (Mo), tungsten (W), or an alloy thereof disclosed in Japanese Patent Application Laid-Open No. 2011-042560, the present inventors have grown the sapphire single crystal. The reason why the later sapphire single crystal could not be removed from the crucible was examined. As a result, in the crucible made of molybdenum, the difference in thermal expansion coefficient between sapphire and molybdenum is not sufficient, so that the tightening of the sapphire single crystal due to the shrinkage of the crucible has not been sufficiently eliminated, while the crucible made of tungsten and molybdenum For the alloy crucible made of tungsten, there is no problem in the coefficient of thermal expansion, but in the portion of the grown sapphire single crystal where the upper surface is in contact with the inner peripheral surface of the crucible, It was found that the cause of the crystal sticking was the cause.

  Based on this knowledge, the present inventor has conducted extensive research on a crucible for growing a sapphire single crystal. As a result, tungsten (on the inner peripheral surface of the crucible is in contact with at least the upper surface of the sapphire raw material melt. By forming an alloy layer (an anti-adhesion layer) made of an alloy of W) or a component constituting a tungsten alloy and a metal element M such as platinum (Pt), palladium (Pd), rhodium (Rh), etc. Obtaining knowledge that the inner peripheral surface and the sapphire material melt can be prevented from sticking, the present invention has been completed. In addition to tungsten, the components constituting the tungsten alloy include, but are not limited to, molybdenum, tantalum (Ta), iridium (Ir), and the like.

(1) Crucible for growing a sapphire single crystal Hereinafter, the crucible for growing a sapphire single crystal according to the present invention will be described in detail by dividing it into a crucible body and an anti-adhesion layer.

(1-1) Crucible body The material of the crucible for growing a sapphire single crystal of the present invention has a melting point higher than the melting point of sapphire (2040 ° C.), specifically, a melting point of 2400 ° C. or higher. It is necessary to have a property.

In addition, as shown in FIG. 4, sapphire has a thermal expansion coefficient (linear expansion coefficient) in the direction perpendicular to the c-axis, which is the growth direction, of about 8 × 10 ⁻⁶ / ° C. at 2040 ° C. For this reason, as a material of the crucible for growing a sapphire single crystal of the present invention, the thermal expansion coefficient at 2040 ° C. is lower than the thermal expansion coefficient in the direction perpendicular to the c-axis of the sapphire single crystal, that is, 8 × 10. ^-6 / ℃ or less is required.

As materials having such a melting point and a thermal expansion coefficient, various materials are conceivable, but considering costs, workability, etc., tungsten (melting coefficient: 3422 ° C., thermal expansion coefficient at 2050 ° C .: 7.0 × 10 ^-6 / ℃) is optimal. In addition, a tungsten-molybdenum-based alloy containing 30% by mass or more of tungsten also has a sufficiently high melting point and a thermal expansion coefficient sufficiently lower than that of sapphire. Can be used.

  On the other hand, refractory metals such as tantalum (melting point: 3017 ° C.), iridium (melting point: 2466 ° C.) and alloys thereof have a larger coefficient of thermal expansion than sapphire, so that the main material of these crucible bodies is However, depending on the use and size of the crucible, it is possible to add these refractory metals in a range where the thermal expansion coefficient of the crucible body does not exceed the predetermined value.

  When an alloy composed of tungsten and molybdenum is used as the material for the crucible body, the content of tungsten is preferably 30% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more. If the tungsten content is less than 30% by mass, the difference between the thermal expansion coefficient of the alloy composed of tungsten and molybdenum and sapphire cannot be made sufficiently large. There is a possibility that the grown sapphire single crystal cannot be easily taken out from the crucible by tightening or the like.

  The shape of the crucible for growing a sapphire single crystal of the present invention is not particularly limited. For example, from the viewpoint of easily taking out the grown sapphire single crystal, as shown in FIG. It can be set as the shape where the taper was formed. In this case, the taper is more preferably provided on the inner peripheral surface of the crucible body so that the inner diameter on the opening side is approximately 1% to 20% wider than the inner diameter on the bottom surface side.

The thickness of the crucible is appropriately selected depending on the size of the sapphire single crystal to be grown. For example, when growing a sapphire single crystal having an outer diameter of 100 mmφ to 200 mmφ and a height of 100 mm to 300 mm , The thickness is preferably 5 mm to 30 mm, and more preferably 10 mm to 20 mm. If the thickness is less than 5 mm, the strength of the crucible cannot be maintained sufficiently. On the other hand, if it exceeds 30 mm, the workability at the time of taking out the grown sapphire single crystal deteriorates due to the weight increase of the crucible, which is not preferable.

  In this case, the dimensions of each part of the crucible other than the thickness are not particularly limited, and may be appropriately selected according to the arrangement and output of the heater, the shape of the melting furnace, and the like.

(1-2) Anti-adhesion layer The crucible for growing a sapphire single crystal of the present invention has an anti-adhesion layer on at least a portion of the inner peripheral surface that is in contact with the upper surface of the sapphire raw material melt during the growth of the sapphire single crystal. Is formed. This anti-adhesion layer is an alloy of a component constituting tungsten or a tungsten alloy and 5% by mass or more of a metal element M (M is one or more elements selected from Pt, Pd, Re, Rh, and Ir). It is comprised by the alloy layer which consists of. The content of tungsten on the surface of the anti-adhesion layer is 20% by mass or more, the content of the metal element M is 20% by mass or more, and the thickness of the anti-adhesion layer is in the range of 0.05 μm to 50 μm. is there.

  In the present invention, as will be described later, after forming a coating layer made of the metal element M on the inner peripheral surface of the crucible, the coating layer is subjected to a heat treatment to diffuse the metal element M into the crucible body which is a base material. By doing so, the component of the crucible body and the metal element M are alloyed to form an anti-adhesion layer. In the present invention, when specifying the presence and thickness of the anti-adhesion layer, the anti-adhesion layer is defined as a region from the surface of the anti-adhesion layer to a position where the content of the metal element M is 5% by mass. Is done.

  In this region, it is preferable that the alloy layer (adhesion prevention layer) is formed by uniformly diffusing the metal element M or by diffusing with a constant concentration gradient. Even if there is a variation in the thickness of the anti-adhesion layer, the content of tungsten on the surface of the anti-adhesion layer is 20% by mass or more and the content of the metal element M is 20% by mass or more. The melting point can be higher than the melting point of sapphire (2040 ° C.), and the sapphire single crystal is effectively prevented from adhering to the inner peripheral surface of the crucible at the portion where the upper surface of the sapphire single crystal is in contact. It becomes possible to do.

  Further, the place where the sapphire single crystal and the inner peripheral surface of the crucible are fixed is limited to the portion where the upper surface of the sapphire raw material melt contacts the inner peripheral surface of the crucible and the vicinity thereof during the growth of the sapphire single crystal. Therefore, it is sufficient that the anti-adhesion layer is formed only on a portion of the inner peripheral surface of the crucible that may come into contact with the upper surface of the sapphire raw material melt. This portion is determined by the amount of sapphire single crystal charged into the crucible, but is about 90% to 95% from the upper end with respect to the height of the crucible. In consideration of fluctuations in the charged amount, it is preferable to form an anti-adhesion layer in the range of 10% to 30% with respect to the height of the crucible, centering on the portion in contact with the upper surface of the sapphire raw material melt. However, when the anti-adhesion layer is locally formed, an operation such as masking is required as will be described later, which may hinder cost reduction. Therefore, the anti-adhesion layer may include a portion where the sapphire raw material melt may come into contact with the upper surface, and may be formed in a wide range of the inner peripheral surface of the crucible. Further, as shown in FIG. You may form in the whole inner surface of.

  The content of tungsten on the surface of the anti-adhesion layer is 20% by mass or more, preferably 20% by mass to 80% by mass, more preferably 20% by mass to 50% by mass, and still more preferably 20% by mass to 30% by mass. . When the content of tungsten is less than 20% by mass, the anti-adhesion layer has a melting point lower than that of sapphire, or the adhesion between the crucible body and the anti-adhesion layer becomes insufficient, and the anti-adhesion layer peels off. there is a possibility. On the other hand, the upper limit of the content of tungsten is about 80% by mass in relation to the content of the metal element M.

  The content of the metal element M is 20% by mass or more, preferably 20% by mass to 80% by mass, and more preferably 40% by mass to 60% by mass. When the content of the metal element M is less than 20% by mass, the sapphire single crystal cannot be prevented from sticking. On the other hand, the upper limit of the content of the metal element M is about 80% by mass in relation to the content of tungsten.

  The content of each component on the surface of the anti-adhesion layer is determined by measuring the content of each component with an electron beam microanalyzer at five positions on the inner peripheral surface of the crucible where the anti-adhesion layer is formed. Can be obtained by arithmetically averaging them.

As the metal element M, one or more selected from platinum (Pt), palladium (Pd), rhenium (Re), rhodium (Rh), and iridium (Ir) can be used.

  Among these, rhenium (melting point: 3186 ° C.) and iridium (melting point: 2466 ° C.) having a melting point higher than the growth temperature of the sapphire single crystal can be used as a coating layer without being alloyed. From the viewpoint of preventing the coating layer from peeling from the crucible body during the growth of the sapphire single crystal in a high temperature environment, it is necessary to alloy it.

  On the other hand, platinum (melting point: 1768 ° C.), palladium (melting point: 1555 ° C.), rhodium (melting point: 1964 ° C.) having a melting point lower than the growth temperature of the sapphire single crystal is alloyed with tungsten constituting the crucible body. Is essential.

  The thickness of the anti-adhesion layer is the minimum that can prevent the adhering of the sapphire single crystal from the viewpoint of reducing the amount of noble metal used, reducing the load when forming the anti-adhesion layer, and reducing the cost. It is preferable to control within the range. Specifically, the thickness of the anti-adhesion layer is 0.05 μm to 50 μm, preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 1 μm. When the thickness of the anti-adhesion layer is less than 0.05 μm, the effect of preventing the sapphire from adhering cannot be obtained. On the other hand, when the thickness exceeds 50 μm, not only the load of the alloying process becomes high, but also the manufacturing cost of the crucible increases.

  As described above, the thickness of the anti-adhesion layer is defined as the distance from the surface of the anti-adhesion layer to the position where the content of the metal element M is 5% by mass. The thickness of the anti-adhesion layer can be determined by performing a line analysis on the content of the metal element M in the crucible cross section using an electron beam microanalyzer. However, when the thickness of the anti-adhesion layer varies, the positions at which the content of the metal element M is 5% by mass are measured from the surface of the anti-adhesion layer at five locations on the observation cross section. The arithmetic average value is defined as the thickness of the anti-adhesion layer.

(2) Manufacturing method of crucible for growing sapphire single crystal Of the manufacturing method of the crucible for growing sapphire single crystal of the present invention, means for manufacturing the crucible body is not particularly limited, and powder metallurgy method, etc. It is possible to manufacture by the conventional technique. For this reason, description of the manufacturing method of a crucible main body is abbreviate | omitted below, and the means and procedure for mainly forming an adhesion prevention layer are demonstrated.

  First, a coating layer made of a metal element M (M is one or more elements selected from Pt, Pd, Re, Rh, and Ir) is formed on the entire or part of the inner surface of the crucible. However, when the content of tungsten on the surface of the anti-adhesion layer is less than 20% by mass after the formation of the anti-adhesion layer, a coating layer composed of the metal element M and tungsten is formed. The formation of this coating layer is not particularly limited. For example, any of wet film formation methods such as electroless plating and electroplating, or dry film formation methods such as sputtering and vacuum vapor deposition may be used. Can do.

  Basically, the thickness of the coating layer is appropriately selected according to the composition of the anti-adhesion layer and the target thickness.

  In addition, when forming a coating layer only on a local portion of the inner peripheral surface of the crucible, that is, a portion where the inner peripheral surface of the crucible and the upper surface of the sapphire material melt are in contact with each other in advance, masking is performed on other portions. It is necessary to do.

  After forming the coating layer, the coating layer is subjected to heat treatment at a heating temperature of 1100 ° C. to 2300 ° C. and a heating time of 1 hour to 10 hours, and the metal element M is diffused near the surface of the crucible. Then, an anti-adhesion layer is formed. When the heating temperature is less than 1100 ° C. or when the heating time is less than 1 hour, the metal element M cannot be sufficiently diffused near the surface of the crucible body. On the other hand, when the heating temperature exceeds 2300 ° C. or when the heating time exceeds 10 hours, the content of the metal element M in the anti-adhesion layer increases, and the thermal expansion coefficient of the anti-adhesion layer and the crucible body This is not preferable because of the large difference.

  Hereinafter, the present invention will be described in detail using examples. In addition, about the crucible produced in the present Example, it evaluated from the following viewpoints.

(A) Anti-adhesion layer After carrying out the dissolution test described later, the anti-adhesion layer formed on the crucible was visually observed to evaluate the state of the anti-adhesion layer. Specifically, the case where the anti-adhesion layer was melted or peeled was evaluated as “defective (×)”, and the case where melting or peeling did not occur was evaluated as “good (◯)”.

(B) Sapphire single crystal After taking out the sapphire single crystal from the crucible, the effect of forming the anti-adhesion layer was confirmed by visually observing the sapphire single crystal. Specifically, when the sapphire single crystal is fixed to the crucible or cracked when taken out, it is evaluated as “defective (×)”, and when the sapphire single crystal is not fixed or cracked, “good (◯)”. "

Example 1
[Production of crucible for sapphire single crystal growth]
A tungsten crucible (1) for growing a sapphire single crystal having a shape as shown in FIG. 1 was prepared. The crucible (1) has an inner diameter of 153 mm on the opening side (2), an inner diameter of 150 mm, a thickness of 5 mm and a height of 150 mm on the bottom side (3), and an inner diameter of the opening side (2) is on the bottom side. It was tapered so as to be 2% wider than the inner diameter of (3). The crucible (1) was manufactured by a powder metallurgy method.

  Specifically, the sapphire single crystal is grown so as to include a portion (contact portion; 6) that is in contact with the upper surface of the sapphire raw material melt (5) in (4) of the inner peripheral surface of the crucible. Inside, a coating layer having a thickness of 0.014 μm made of platinum was formed by a plating method over a range of 20 mm in the vertical direction with reference to a portion possibly contacting the upper surface of the sapphire raw material melt. Thereafter, the crucible (1) was heat-treated at a heating temperature of 1600 ° C. and a heating time of 2 hours, thereby diffusing platinum in the vicinity of the surface of the crucible (1) to form an anti-adhesion layer (7) (FIG. 2).

  Further, a coating layer is formed on a test piece made of the same material and the same thickness as the crucible (1) under the same conditions, and the anti-adhesion layer (7) is formed by heat treatment under the same conditions. did. As a result of observing the cross section of this test piece with an electron probe microanalyzer (EPMA), the thickness of the anti-adhesion layer (7) containing 5% by mass or more of platinum was 0.06 mm from the surface of the alloy piece. there were. The amount of tungsten and the amount of platinum on the surface of the anti-adhesion layer were 77% by mass and 23% by mass, respectively.

[Dissolution test]
Into the sapphire single crystal growth crucible thus obtained, 2 kg of alumina was put and melted by heating to about 2100 ° C. using a resistance heating type melting furnace using a carbon heater. Then, the sapphire single crystal was obtained by cooling in a furnace.

  After confirming that the temperature in the furnace had dropped to room temperature, the crucible was taken out, the crucible was turned upside down, and a light impact was applied to take out the sapphire single crystal. The sapphire single crystal was not fixed to the crucible surface, and no cracks were generated. Moreover, neither fusion nor peeling was confirmed in the anti-adhesion layer after taking out the sapphire single crystal.

(Examples 2-18, Comparative Examples 1-9)
A crucible for growing a sapphire single crystal was produced in the same manner as in Example 1 except that the crucible material, the metal constituting the coating layer, the temperature and time of the heat treatment were changed to the conditions shown in Table 1.

  Using these crucibles for sapphire single crystal growth, the same dissolution test as in Example 1 was performed, and evaluation was performed from the viewpoint of (a) an anti-adhesion layer and (b) a sapphire single crystal. These results are shown in Table 1.

(Comprehensive evaluation)
Examples 1 to 18 are examples using crucibles for growing a sapphire single crystal belonging to the technical scope of the present invention. Since the sapphire single crystals obtained in Examples 1 to 18 were not fixed to the crucible, they could be easily taken out from the crucible. Further, the sapphire single crystal taken out was not cracked. Furthermore, as a result of observing the inner peripheral surface of the crucible after taking out the sapphire single crystal, it was confirmed that the adhesion preventing layer did not melt or peel off.

  Comparative Example 1 is an example in which the anti-adhesion layer was not formed. For this reason, a part of the grown sapphire single crystal is fixed to the crucible, and the sapphire single crystal cannot be taken out from the crucible without destroying the crucible.

  Comparative Examples 2 and 3 are examples in which the thickness of the anti-adhesion layer is thinner than the range specified in the present invention, and in Comparative Examples 4 and 5, the content of the metal element M on the surface of the anti-adhesion layer is specified in the present invention. This is an example that is less than the range to be used. In either case, as in Comparative Example 1, a part of the grown sapphire single crystal was fixed to the crucible, and the sapphire single crystal could not be easily taken out from the crucible. Further, the sapphire single crystal taken out was cracked.

  Comparative Examples 6 and 7 are examples in which the thickness of the anti-adhesion layer exceeds the range specified in the present invention. In Comparative Examples 6 and 7, the sapphire single crystal after growth was not fixed or cracked, and the anti-adhesion layer was not melted or peeled off. However, the amount of platinum or palladium used could not be reduced sufficiently. The manufacturing cost could not be reduced sufficiently.

  Comparative Examples 8 and 9 are examples in which the content of tungsten on the surface of the anti-adhesion layer is less than the range defined in the present invention. For this reason, in any of the comparative examples, tungsten and the metal element M were not sufficiently alloyed, the metal element M was melted, and the sapphire single crystal was fixed at the melted portion.

DESCRIPTION OF SYMBOLS 1 Crucible for sapphire single crystal growth 2 Opening side 3 Bottom side 4 Inner peripheral surface 5 Sapphire material melt 6 Contact part 7 Adhesion prevention layer

Claims (6)

It is made of tungsten or an alloy containing tungsten having a melting point of 2400 ° C. or more and a thermal expansion coefficient at 2040 ° C. of 8 × 10 ⁻⁶ / ° C. or less. A sticking prevention layer for preventing sticking between the inner peripheral surface and the sapphire raw material melt is formed on a portion in contact with the upper surface of the sapphire raw material melt,
The anti-adhesion layer is composed of an alloy of a component constituting tungsten or a tungsten alloy and a metal element M of 5% by mass or more, and M is selected from Pt, Pd, Re, Rh, Ir More than species,
The content of tungsten on the surface of the anti-adhesion layer is 20% by mass or more, and the content of the metal element M is 20% by mass or more,
The thickness of the anti-adhesion layer is 0.05 μm to 50 μm,
A crucible for growing sapphire single crystals.
2. The crucible for growing a sapphire single crystal according to claim 1, wherein the crucible body is made of an alloy containing tungsten, and the alloy containing tungsten is made of an alloy of tungsten and molybdenum.   The crucible for growing a sapphire single crystal according to claim 1, wherein the sticking prevention layer has a thickness of 0.1 μm to 10 μm.   The crucible for growing a sapphire single crystal according to claim 1, wherein the tungsten content on the surface of the anti-adhesion layer is 20 mass% to 50 mass%.   The crucible for growing a sapphire single crystal according to claim 2, wherein the tungsten content in the alloy of tungsten and molybdenum is 30% by mass or more. It is a manufacturing method of the crucible for sapphire single crystal growth in any one of Claims 1-5 , Comprising: 1 type selected from Pt, Pd, Re, Rh, Ir on the whole surface or a part of the inner surface of the said crucible main body the metal element M is more elements, or form a coating layer comprising a metallic element M and tungsten, with respect to the coating layer, 1100 ° C. to 2300 ° C. the heating temperature, 1 hour to 10 hours heating time A method for manufacturing a crucible for growing a sapphire single crystal, wherein the anti-adhesion layer is formed by performing the heat treatment described above and diffusing the metal element M in the crucible body.

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